DESIGN AND FORMATION OF SILICON MEMBRANES FOR ACOUSTIC SENSORS
Abstract
Micromechanical acoustic transducers based on membranes have been used in medical diagnostic
systems, range finders, hydroacoustics, as well as in biometric security systems. The
range of tasks solved by such devices is constantly expanding, the requirements for increasing the
measuring range, accuracy, reducing the size and energy consumption are increasing. In addition,
many acoustic applications require sensor arrays integrated with electronic signal processing
systems. These features have determined the need for the use of micro-processing methods for
their industrial production. The aim of this work is to design and form silicon membranes for
acoustic sensors with operating ranges of resonant frequencies from 10 kHz to 100 MHz and pressures
from 0.1 to 1000 kPa. In this paper, the design of single-crystal silicon membranes for preparation
by anisotropic liquid etching is evaluated. Analytical dependences of pressure and resonance
frequency on geometrical parameters of membranes are presented. We defined the ranges
of the thickness (10–50 microns) and the length of the fin membranes (200-600 microns). The topology
of the photomask for the manufacture of such membranes is calculated. Experimental studies
of the etching of the si plate with a solution of 30% KOH were carried out and the etching rate
was found to be 1.25±0.1 μm/min. Anisotropic liquid etching was used to form silicon membranes
of quadrate shape with thickness of 50 μm with fin lengths from 200 to 250 μm with resonant frequencies
in the range from 1.9 to 3 MHz. The results obtained could be used in the development of
acoustic sensors made of monocrystalline silicon.
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